Time-lapse photography of clouds and other atmospheric phenomena

Time-lapse photography is a process in which  a camera takes a picture at a given interval for a certain period of time. The result of this process can be either a folder with a series of images which can be viewed as a rapid slideshow, or a single movie file which was created from these individual images using dedicated software. Regardless of whether we use a slideshow or movie file to visualize the captured images, we review the images at a much higher speed than they were originally captured. Processes which under normal circumstances are rather slow get set into motion with time-lapse photography  - e.g. formation and decay of clouds, sunsets and sunrises, polar lights, plant growth or blossom of flowers, cell splitting and growth of microorganisms, construction of buildings, traffic in a city, and many others. Images from geostationary weather satellites, when shown as movies or loops, can also be considered a special type of time-lapse imaging, though taken by much more expensive and sophisticated technology (which we will not discuss here). Time-lapse sequences can be taken either for scientific and educational purposes, or just for fun.

There are several ways to capture a time-lapse sequence, each having its own advantages and disadvantages. We will specifically focus on capturing clouds and various other atmospheric phenomena; however, most of the issues discussed below can be applied in general. What makes time-lapse photos of clouds unique compared to other targets is the speed of cloud evolution and motion, which demands time-lapse intervals on the order of several seconds. For most of the cloud types the optimal interval is about 5 seconds, but for rapidly changing clouds we may need to go down to about 1 second, while on other occasions 10 seconds is just fine. Thus the ability of a camera to shoot time-lapse at intervals between 1 and 10 seconds is our first, most important camera feature. Most of the clouds we wish to capture by time-lapse photography occupy large portions of the sky, so a wide angle lens is another important feature. In most cases a 28 mm lens will suffice (35 mm film camera equivalent), but in some cases we may need even wider lens (24 mm or shorter). Since the evolution and motion of clouds usually result in significant changes of brightness distribution over the frame and time, we need to fix the camera exposure somehow - either by "freezing" the exposure by AE lock, or preferably by full manual exposure control of the camera (M mode). Finally, the last feature which may be helpful is manual focus of the camera, or an option to lock the lens to pre-defined infinity. This bypasses a potential problem in some cameras when attempting to focus on clouds, and also saves the camera's energy supply.

There are two basic methods of time-lapse photography:

1. Control of the camera from an external device. This device can be either a computer (in order to shoot the time-lapse sequences outdoors, this should ideally be a laptop or pocket-sized device), or a special piece of hardware designed and constructed specifically for this purpose (external remore timer). This category includes either web cameras uploading their images directly to the steering computer, or computer-control-enabled digital cameras of both categories - compact and DSLR types. It should be noted here that shutters of cameras have a limited lifetime (shorter for larger-sized DSLR cameras), so you might prefer a cheaper compact type of camera rather than an expensive DSLR. When using digital cameras, the captured images may be stored either on a memory card of the camera itself, or directly on a hard disc of the steering computer.
    

2. Internal time-lapse feature of the camera itself. This is my preferred type. All you need is the camera itself, a good steady tripod, and a supply of batteries and memory cards; you are then ready to shoot time-lapse wherever you go - hiking, mountaineering, or any other place where you happen to be without your computer. Although there are many cameras with this option, the shortest interval is usually 1 minute or 30 seconds, which is still too long for clouds :-((  Only very few cameras go to shorter basic intervals - most of recent Ricoh cameras have a time-lapse option (called interval shooting by Ricoh) starting at 5 seconds, allowing an unlimited number of shots to be taken within one sequence. From Ricoh cameras, the best choices are Ricoh GX100, GX200, GR Digital II, GR Digital III or GXR, or some of their cheaper models, e.g. Ricoh R6, R8, R10, CX1, CX2 and CX3 cameras, all of these supporting the large capacity SDHC memory cards. More about using the Ricoh cameras for time-lapse purposes here.
   
   Besides Ricoh, also the Kodak P-series cameras (all of them already discontinued) had the time-lapse option, e.g. Kodak P880. This was my first time-lapse camera which I used in 2006 and 2007 – it has a great wide-angle lens (24 mm equiv.), very good colors and excellent exposure dynamics, its time-lapse starts at 10 second interval, but has a limit of 99 shots :-(( The limit means that for longer sequences you have to launch the time-lapse mode over and over again, every 16.5 minutes - which was the principle disadvantage of this camera. The 99-shots limit was the main reason why I decided to switch to Ricoh GX100 (in December 2007).
   
   The 10-second interval can be found at some of the recent Pentax compact cameras (limited by 999 shots in one series), and even shorter intervals (down to 1 s) are offered by some of the Nikon DSLRs. Alternatively, you can also use most of the Canon PowerShot cameras in combination with CHDK software run from the camera's memory card, but this may not be that easy. With increasing power of camera processors and decreasing write-time of captured images, the list of cameras suitable for time-lapse photography of clouds will hopefully grow.

In principle, you can also use the continuous shooting mode of a camera for time-lapse photography; however, due to the speed of this mode (usually between 1 to 2 shots every second) you run out of power and memory card space quite quickly. Some DSLR cameras enable one to slow down the speed of the continuous mode by pre-setting a mirror lock time, but given the limited durability of their shutters I would rather avoid using these for time-lapse too often.

 Other camera features you should consider when selecting the one for time-lapse photography are:

• type of the tripod mount - you may damage it rather quickly if it's made of plastic, so metal ones are preferred;
• possibility of replacing the battery and memory card when the camera is attached to a tripod;
• option to power the camera from an external power adapter (100/240V, or 12V);
• number of shots you can take on a single battery charge;
• picture dynamics - ability to capture a wide range of illuminated objects, from dark to bright ones (clouds are usually VERY bright, most of cameras tend to overexpose these at regular settings);
• and of course, the maximum size of a memory card the camera can use - the larger, the better.

Finally, when creating a movie file from a sequence of images, you will need software which can do this for you. First you will need to resize the original images to a movie file format - of course you can shoot the images directly into the final smaller size, but I prefer to shoot to the larger file size and resize/crop the images afterwards (I use Adobe Photoshop for this step). Next, you need a tool to create the movie file from the static images. There are more options for this - I use RAD Video Tools to construct the AVI files, VirtualDub for their processing and tuning (if needed), TMPGEnc to convert these into MPEG1 files, MPEG Streamclip or QuickTime 7 Pro for QuickTime H.264/MOV conversion, or MediaCoder into H.264/MP4 format. For details about creating the movie file from a sequence of images see my step by step guide.

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